Chronic amphetamine tolerance and reverse tolerance are studied in relation to neurotransmitter function in several areas of the rat brain. Behavioral assays selected to reflect mood altering and psychosis producing effects of the drug in humans include self-stimulation behavior (tolerance) and locomotor stimulation and stereotypy (reverse tolerance). Biochemical measures involve dopamine turnover and receptor binding characterization. Behavioral and biochemical correlates are based on different acute and chronic dosage regimens, a challenge dosage test, and recovery times.